This invention relates to a distributed processing message delivery system operable for controlling the distribution of variable length messages between processors.
In communication systems (or other types of control systems) it is typical for numerous messages to pass between a central processor and any number for remote processors. These remote processors, for example, may be located on interface boards and serve to control a number of individual ports or telephone stations. For each transaction, e.g., an off-hook at a calling station, many individual functions must be changed at the station. These functions may include the changing of the lamp information, ringing status, or delivery of specialized messages such as "All Lines Busy" on alpha-numeric displays. The ability of the central processor to pass each of the messages to the various remote processors for subsequent control of the individual ports or stations affects the call capacity of the processor.
Another problem faced by such systems is that each message requires considerable processor overhead in formatting for delivery to the remote processors. This overhead includes the addition of header information containing the address of the desired remote processor, and the addition of checksums at the end of the message to insure proper delivery of the message. All of this requires valuable processor time, and when the message size is small, this overhead must be expended for each message. Thus, when multiple small messages are destined for the same remote processor, valauble time is wasted in formatting the messages.
One solution to the problem would be to send a single message to each station containing all of the necessary information. However, such a solution proves difficult in that there is a variable number of messages which must be communicated, each message having a variable number of bytes of information. For example, ringing information may be conveyed with a few bits, while lamp information may require several 8-bit bytes. The size of a display message, of course, depends upon the number of information characters to be displayed at the telephone console. Thus, using a single fixed size message packet having a fixed number of bytes would be wasteful of bandwidth.